Corrosion evaluation device and corrosion evaluation method

Abstract

A corrosion evaluation device for performing a quantitative evaluation of corrosion by measuring a quantity of decrease in the thickness of a magnetic material which is covered by a non magnetic material or a magnetic material which is not covered by a non magnetic material which includes: a magnetic field generating device for generating such a magnetic field that includes the magnetic material in a magnetic path, a Giant Magnet-Resistive effect (GMR) sensor provided with a GMR sensor for detecting a magnetic flux leakage with regard to the magnetic material and converts a change in the magnetic flux into an electrical signal, a thickness reduction calculation portion for calculating a quantity of decrease in the thickness of the magnetic material based on the electrical signal. The corrosion evaluation device precisely performs a quantitative evaluation of corrosion even when the magnetic material, which is to be evaluated, is covered by a non magnetic material.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application is a 35 U.S.C. §371 National Phase conversion of PCT / JP2006 / 325172, filed Dec. 18, 2006, which claims priority of Japanese Application No. 2005-364387, filed Dec. 19, 2005, and Japanese Application No. 2006-309165, filed Nov. 15, 2006, the disclosures of which have been incorporated herein by reference. The PCT International Application was published in the Japanese language.TECHNICAL FIELD[0002]The present invention relates to a corrosion evaluation device and a corrosion evaluation method.BACKGROUND ART[0003]A Magnetic Flux Leakage Method (MFL), which measures quantity of decrease in the thickness of the steel material by adding a magnetic field to the steel material and detecting a change of magnetic flux leakage, has been conventionally used as one of the methods to quantitatively evaluate the progress of corrosion in steel material (magnetic material) which are used for pipelines of oil or gas, a bottom plate ...

AI Technical Summary

Benefits of technology

The present invention solves the problem of accurately evaluating corrosion on magnetic materials that are covered by non magnetic materials such as concrete or the like. The invention uses a GMR sensor with higher magnetic sensitivity than a hall element to precisely detect the magnetic flux leakage and calculate the quantity of decrease in the thickness of the magnetic material. This allows for quantitative evaluation of corrosion and enables the use of a reinforcing steel or steel plate as a magnetic material for corrosion evaluation. The invention can be implemented in a corrosion evaluation device that includes a magnetic field generating device, a GMR sensor, a thickness reduction calculation device, and a distance between the surface of the magnetic material and the GMR sensor can be maintained constant or moved.

Problems solved by technology

Now, in the magnetic flux leakage method that used a hall element as a magnetic sensor, because magnetic sensitivity of the hall element is weak, when the steel material, which is an object to be evaluated, is covered by a non magnetic material such as concrete or the like, it was not possible to precisely detect the magnetic flux leakage and so it was difficult to perform quantitative evaluation of corrosion.

That is, a ruptured portion of the steel material covered by a non magnetic material such as concrete or the like can be detected, but it is not possible to perform quantitative evaluation of corrosion.

However, these methods can determine the presence of corrosion, but quantitative evaluation cannot be performed.

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